This invention relates to methods and apparatus for adhesively fastening friction liners in place, in particular on an annular support plate, in a component such as an automotive clutch.
At the present time, friction liners are used for example in the manufacture of friction discs, especially for dry clutches for motor vehicles. A friction disc generally comprises a support plate in the form of an annular ring having an outer peripheral portion which is divided into radial blades. These blades have a central fastening portion, bounded by cranked or bent portions of the plate, which is joined to the central portion of the plate through a tangential cranked portion which forms the foot of the blade.
This tangential cranked portion offsets the central fastening portion axially with respect to the general plane of the central part of the support plate. Friction liners are secured on either side of the outer peripheral portion.
Fastening of the liners on the radial blades can be achieved for example by riveting or adhesive bonding, by a method which is described in U.S. Pat. No. 6,102,184 and the corresponding published international patent specification W098/44272A. That method comprises an adhesive applying step which consists in depositing a predetermined quantity of adhesive on an adhesion zone positioned on the lateral fastening face of the radial blade.
Where adhesive bonding of the friction liners is used, the quality of deposition of the adhesive is very important. In this connection, the friction discs are subjected to very high stresses in use. The quantity and distribution of the adhesive at the interface between the radial blades of the support plate and the friction liners are critical factors in the mechanical strength and consistency of performance of the friction disc.
Known methods and apparatus for adhesively fastening friction liners on the support disc work on the basis of using a nozzle to deposit a band of adhesive on a fastening face of the blades of the support plate. However, such methods do not enable sufficiently precise control to be achieved in the quantity of adhesive deposited. It often happens that stray particles of excess adhesive will occur, and these can give rise to significant malfunctioning, especially where the blades are of the tripod type and where the excess adhesive is on a support face of a peripheral portion of the blade.
In addition, the known methods and apparatus do not enable reliable quantity control to be exercised on support plates having faulty adhesive application, or those which may have such faults.
With a view to overcoming the above mentioned drawbacks, the invention, in a first aspect thereof, proposes a method of adhesively fastening friction liners on at least one of the lateral fastening faces of the radial blade located on the outer periphery of an annular support plate, the method being of the type which includes an adhesive application step that consists in depositing a predetermined quantity of adhesive on an adhesion zone positioned on the said fastening face of the radial blade, characterised in that the step of depositing adhesive is carried out by means of an adhesive application head which includes an adhesive application zone, the form of which corresponds to that of the adhesion zone on the lateral fastening face of the blade.
Thanks to the invention, the fastening face of the blade does not need to be formed in relief as described in European patent specification No. EP 0 797 017. The application of adhesive is both reliable and economic.
According to a preferred feature of the invention, the adhesive applying step comprises a first phase in which the adhesive applying zone of the applicator head is impregnated with adhesive, and a second phase, or application phase, which consists in bringing the impregnated adhesive applying zone of the applicator head into contact under axial pressure with the adhesion zone on the appropriate face of the blade, whereby to transfer the correct predetermined quantity of adhesive from the head to the blade.
According to a further feature of the invention, during the second phase of the method, a backing or counter-pressure head comes into engagement against the other lateral face of the blade which is opposed to the said lateral fastening face, so that the backing head applies on the said other face an axial force opposed to that exerted by the applicator head on the lateral fastening face, thereby preventing deformation of the blade.
Preferably, the two lateral faces of the blade have adhesive applied simultaneously to them by two respective applicator heads, the application zones of which are arranged in facing relationship with the adhesion zones of each of the lateral fastening faces.
Preferably, the adhesive applying step is followed by rotation of the support plate in such a way as to put the adhesion zone of the fastening face of another radial blade into facing relationship with the adhesive applying zone of the applicator head.
The method preferably also includes a step of controlling the application of adhesive on at least one lateral fastening face.
According to another preferred feature of the invention, an optical system enables the presence of adhesive outside the adhesion zone of the fastening face to be detected; and according to a further feature, an optical system enables the absence of adhesive on at least part of the adhesion zone to be detected.
Where such an optical system detects the presence of adhesive outside the adhesion zone, and/or the absence of adhesive on part of the adhesion zone, the support plate, carrying the incorrectly applied adhesive, is rejected at this stage.
According to a further preferred feature of the invention, such an optical system determines the real position of the adhesion zone, carrying adhesive, on the fastening face of the blade; then it compares this real position with a theoretical position of the adhesion zone, and if these two positions are different, then the support plate, which has been at least partly coated with adhesive, is rejected.
According to a second aspect of the invention, in an apparatus for adhesively fastening friction liners on at least one of the lateral fastening faces of a radial blade projecting at the outer periphery of an annular support plate, the apparatus being of the type that includes means for depositing a predetermined quantity of adhesive on an adhesion zone positioned on the fastening face of the radial blade, the apparatus is characterised in that the means for depositing adhesive comprise at least one adhesive applicator head, having an adhesive applying zone which lifts adhesive in a reservoir or in a shallow recess (or xe2x80x9cfootprintxe2x80x9d), and deposits the predetermined quantity of adhesive on the adhesion zone of the appropriate fastening face of the appropriate blade.
According to a preferred feature of the invention, the applicator head deposits the predetermined quantity of adhesive on the adhesion zone by contact, under axial pressure, of the adhesive applying zone with the adhesion zone of the fastening face.
The apparatus preferably includes a counter-pressure or backing head which is engaged against the lateral face of the blade that is opposed to the lateral fastening face of the latter, and which applies on the said lateral face of the blade an axial force opposed to that exerted by the applicator head on the lateral fastening face, whereby to prevent deformation of the blade.
The apparatus preferably includes means for rotating the support plate in such a way as to put the successive lateral fastening faces of different blades into facing relationship with the applicator head for the purpose of applying adhesive to them.
The drive means preferably include indexing means for positioning the adhesion zone in facing relationship with the adhesive applying zone of the applicator head.
The apparatus preferably includes means for controlling the adhesive zone to which adhesive is applied. These control means preferably comprise an optical viewing device which, in particular, controls the position of the adhesive zone and/or the distribution of adhesive on the lateral fastening face.
According to another preferred feature of the invention, the said control means include a weighing device which controls the quantity of adhesive deposited on at least one adhesion zone of a lateral fastening face of a blade.
The apparatus may include two adhesive applicators, each of which is situated in facing relationship with an adhesion zone on the lateral fastening faces of a blade.
The apparatus may include a reserve supply of adhesive which feeds at least one adhesive reservoir in such a way as to maintain the filling level of the latter at a level greater than a limiting lower level.
The apparatus preferably includes a device for cleaning the adhesive applying zone of at least one adhesive applicator.
Further features and advantages of the invention will appear more clearly from a reading of the following detailed description of some preferred embodiments of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.